In recent years, with a growing demand for conservation of resources in the field of light source devices such as halogen light bulbs and fluorescent lamps, light-emitting devices utilizing LEDs with power-saving capabilities and long life have been provided.
With respect to light-emitting devices that can be used as light sources of various light source devices, an increase in luminance is highly desirable. Proposed as an example of light-emitting devices that achieve the increase in luminance is a light-emitting device including a plurality of LEDs that are arranged on a substrate in a row and are connected with one another (see Patent Literatures 1 and 2).
In a light-emitting device disclosed in Patent Literature 2, a plurality of LEDs are arranged on a substrate in two rows and are connected in series by wires, and all the LEDs and wires are sealed together by a sealing member.
Considered as one example of such a light-emitting device is a light-emitting device 501a having configuration as illustrated in FIG. 18A. In this configuration, a plurality of LEDs 520 are arranged in a row on a substrate 510 in the shape of an elongated rectangular plate. Pairs of electrode pads 541a and 542a are formed on the substrate 510 in one-to-one correspondence to the LEDs 520 such that electrode pads 541a and 542a are provided at opposites sides of a corresponding LED 520 in the widthwise direction of the substrate 510. The electrode pads 541a and 542a are electrically connected to the corresponding LED 520 by wires 595. Each electrode pad 541a is a part of first wiring 541, and each electrode pad 542a is a part of second wiring 542. The LEDs 520 are connected in parallel with one another by the first wiring 541, the second wiring 542, and the wires 595. The LEDs 520 and the pairs of electrode pads 541a and 542a are sealed by a sealing member 530 to prevent oxidation, corrosion, and the like.
In order to mount the LEDs 520 in a limited area on the substrate 510, it is necessary to increase a size of the sealing member 530 in the widthwise direction of the substrate 510 with increasing distance between the LEDs 520 and the respective pairs of electrode pads 541a and 542a in the widthwise direction of the substrate 510. With an increase in size of the sealing member 530, more material for the sealing member 530 becomes necessary, leading to an increase in material cost.
Considered to solve this problem is configuration as illustrated in FIG. 18B. In this configuration, each pair of electrode pads 541a and 542a is provided close to the corresponding LED 520, thereby reducing the size of the sealing member 530 in the widthwise direction of the substrate 510.
On a surface of the substrate 510 on which the LEDs 520 are mounted, an insulating film having a high light reflectance is formed to reflect light emitted from the LEDs 520. The wirings 541 and 542 have a lower light reflectance with respect to light in a visible region than the insulating film formed on the substrate 510. Since each pair of electrode pads 541a and 542a, which are respectively parts of the wirings 541 and 542, is provided close to the corresponding LED 520, and light emitted from the corresponding LED 520 is absorbed by the pair of electrode pads 541a and 542a, a light-extraction efficiency of a light-emitting device 501b is low.
Considered to address this problem is configuration as illustrated in FIG. 18C. In this configuration, a distance WW between the electrode pads 541a and 542a included in each pair is made longer than a distance WN between the electrode pads 541a and 542a included in each pair in the light-emitting device 501b. 
FIGS. 19A and 19B each illustrate distribution of the intensity of light emitted from each LED 520, and a positional relation between the LED 520 and the corresponding pair of electrode pads 541a and 542a. FIGS. 19A and 19B respectively correspond to the configurations as illustrated in FIGS. 18C and 18B. In each of FIGS. 19A and 19B, an area enclosed by an alternate long and short dash line is an area in which the distribution of the intensity of light emitted from the LED 520 is 1/e, which is the maximum light intensity, or more (hereinafter, referred to as an “effective area”.)
When the electrode pads 541a and 542a are located within the effective area as illustrated in FIG. 19B, an average light reflectance in the entire effective area is reduced accordingly, resulting in a decrease in light-extraction efficiency. In contrast, when the electrode pads 541a and 541b are not located within the effective area as illustrated in FIG. 19A, light in the effective area is fully reflected off the insulating film, leading to an increase in light-extraction efficiency.
As described above, the distance WW between the electrode pads 541a and 542a in each pair is longer and thus the average light reflectance in the entire effective area is higher in the light-emitting device 501c as illustrated in FIG. 18C than in the light-emitting device 501b as illustrated in FIG. 18B. As a result, an efficiency of extracting light emitted from the LEDs 520 is higher in the light-emitting device 501c than in the light-emitting device 501b. 
The light-emitting device is typically provided with a protective element to prevent application of overvoltage (e.g. surge voltage) higher than rated voltage to each LED. This is important in terms of ensuring the reliability of the light-emitting device. One example of the protective element is a Zener diode. As with the LEDs, the Zener diode is required to be sealed by the sealing member to prevent corrosion and the like. When a Zener diode 560 is provided for the light-emitting device 501c as illustrated in FIG. 18C, the Zener diode 560 may be located apart, in the widthwise direction of the substrate 510, from the LEDs 520 arranged in a row, for example. In this case, however, since the size of the sealing member 530 increases as described above, the material cost might not be reduced. The Zener diode 560 may be sealed by a sealing member separate from the sealing member 530. In this case, however, it is necessary to add a step of providing the separate sealing member only for sealing the Zener diode 560. This can lead to a decrease in productivity. For the above-mentioned reasons, it is considered reasonable to locate the Zener diode 560 along a row of the LEDs 520 as shown by an arrow of FIG. 18C.